Typical fats and oils provide approximately 6 kcal/g of metabolizable energy compared to 4 kcal/g for protein or carbohydrate [Atwater, W. O. et al., Annu. Rep. Storrs Agric. Exp. Stn. (1903) No.15, 123-146 & Maynard, L. A., J. Nutr. 28 (1944) 443-453]. In addition to the caloric and nutritional value, fats have many functions in the diet. Fats and oils carry, enhance and release the flavours of other food components, delays digestion, increases palatability of food and imparts the feeling of satiety. Certain unsaturated fatty acids like 9,12-octadecenoic acid (linole acid) which are known to be essential fatty acids are necessary as they are not produced in the body. Fats and oils are also associated with the fat-soluble vitamins A, D, E and K, and the absorption of these vitamins is impaired at very low fat intakes. Fat is also associated with diseases such as coronary heart disease and cancer, a high fat diet being positively linked to both. The U.S. Surgeon General has recommended that no more then 30% of the dietary calories should be derived from fat [U.S. Department of Health and Human Services, The Surgeon General's Report on Nutrition and Health, DHHS (PHS) Publication 88-50210, [U.S.GPO., Washington, D.C. (1988)]. Regulatory and advisory bodies advocate a lowered fat intake in order to reduce the incidence and morbidity of many coronary diseases, stroke, high blood pressure, obesity and diabetes.
However, food habits are difficult to change and the positive contribution of fats to increase the palatability of foods is generally recognized. The level of fat in the diet of affluent societies is too high and needs to be lowered. Reduced fat or low calorie foods as well as fat replacers or substitutes have been the result of numerous attempts to meet the health recommendations without changing traditional ways of eating.
Three different types of fat replacers namely carbohydrate-based, protein-based and fat-based are reported in the literature.
Carbohydrate-based fat replacers consists of many products like dextrin, polydextrose, maltodextrin, cellulose, gums etc., which are used as thickeners and stabilizers in frozen desserts, salad dressings, margarine type spreads, baked products, frostings and snacks. Many products based on starch have been developed specifically as fat mimetic [Alexander, R. J., Cereal Food World 40 (1995) 366-368]. However, starch based products are not good for diabetics for whom good glucose control is necessary [Grundy, S. M., Diabetics Care 14 (1991) 796-801]. The U.S. Food and Drug Administration (FDA) regulations state that sensitive individuals may experience a laxative effect from excessive consumption of maltrodextrins [U.S.A. Food & Drug Administration Regulations 21 CFR Part 105]. Some popular examples of carbohydrate based fat replacers are Stellar, Remyrise AP, N-Oil, Lycadex, Maltrin, Ex-cel, Fibercel, Centu Tex, Fibrex etc. [Jones, J. M., Chemistry & Industry, (1996) 494-498].
Protein-based fat replacers are produced using common proteins such as egg white, skimmed milk or whey by microparticulating them into a particle size of 1-3 μm to obtain a slippery and creamy fat like feeling which provide 1-2 kcal/g [Singer, N. S., et al., J.] Amer. Coll. Nutr. 9 (1990) 388-397]. These products are being used in variety of food products such as yogurts, cheese products, frozen desserts and also for formulating low fat baked goods such as cheese cakes and pie crust. Gelatin from fish waste was also reported as a fat replacer to use as a viscosity modifier and to impart a creamy texture. However, such fat replacers are reported to be hypersensitive for persons with allergy to the base proteins [Young, V. R., et al., J. Amer. Coll. Nutr. 9 (1990) 418-426]. Some examples of protein based fat replacers popular in the market are Dairylight, Simplesse, Lita, Calpra 75 etc. [Jones, J. M., Chemistry & Industry (1996) 494-498].
Carbohydrate-based and protein-based fat replacers are presently used in a range of foods, and are effective in delivering fat-like texture where the final product has a significant water content and is not exposed to extremely high temperatures or temperature variations [Mela, D. J., Fett/Lipid 98 (1996) 50-55]. These problems can be overcome by fat-based low calorie fats.
Fat-based low calorie fats have many advantages like functional and sensory properties very similar to the normal fats when compared to the carbohydrate and protein-based fat replacers. They also provide both the characteristic texture and flavour effects of native fats.
Many fat-based low calorie fats are reported in the literature namely propoxylated glycerols esterified with fatty acid chlorides [Masten, L. W., EP 571,219 (1993); White, J. F. et al., EP 325,010 (1989)]; fatty acid diesters of C4-10 dihydric alcohols [Klemann, L. P. et al., U.S. Pat. No. 5,286,512 (1994); Klemann, L. P. et al., U.S. Pat. No. 5,006,351 (1991)]; trioltriester derivatives [Klemann, L. P. et al., U.S. Pat. No. 5,043,179 (1991)]; polyol fatty acid polyesters [Kester, J. J. et al., U.S. Pat. No. 5,314,707 (1994); Letton, J. C., et al., U.S. Pat. No. 5,306,514 (1994)]; polyvinyloleate [D' Amelia, R. P. et al., U.S. Pat. No. 4,915,974 (1990)]; oleoylloeate [Jacklin, P. T. et al., U.S. Pat. No. 4,915,974 (1990)]; bis-oleoylaspartyladipare [Klemann, L. P. et al., U.S. Pat. No. 5,139,807 (1992)]; esterified alkoxylated mono- and diglycerides [Cooper, C. F. et al., U.S. Pat. No. 5,371,253 (1994)]; triglycerides containing C12-22 fatty acids having alkyl groups at least at the position 5,9,13 of the alkyl chain [Tagiri, M. et al., JP 04,325,055 (1992)]; 1,3-didecanoylglycerol [Mazur, A. W. et al., U.S. Pat. No. 5,137,660 (1992)]; alkyl or polyol thioesters [Klemann, L. P., U.S. Pat. No. 4,992,293 (1991)]; propyleneglycol diesters of medium chain and long chain saturated fatty acids [Stipp, G. K. et al., EP 495,553 (1992)]; alkylmalonic acid diesters [Fulcher, J. G. et al., Aus. Pat. 594,040 (1990)]; esterified polyoxyalkylene block co-polymers [Cooper, C. F. et al., EP 481,717 (1992)]; alkylglycoside fatty acid polyesters [Winter, D. D. et al., U.S. Pat. No. 4,942,054 (1990)]; fatty acid esters of sucrose [Letton, J. A., et al., EP 375,027 (1990)]; sorbitol fatty acid esters [Gruetzmacher, G. D., EP, 591,258 (1994)]; partially esterified polysaccharide with fatty acids [White, J. F. U.S. Pat. No. 4,959,466 (1990)]; alkoxylated sugar and sugar alcohol esters [Ennis, J. L. et al., EP 425,635 (1991)]; polysaccharide fatty acid polyester [Meyer, R. S. et al., U.S. Pat. No. 4,973,489 (1990)]. All these are unnatural compounds not normally encountered in human diet and the long term affects of consumption of such are presently unknown.
Examples of the more commonly known low calorie fats are OLESTRA™, medium chain triglycerides (MCTs), Caprenin and SALATRIM™. OLESTRA™ is a mixture of hexa-, hepta-, and octa-fatty acid esters of sucrose. The physical properties of sucrose polyesters are similar to normal triglycerides [Jandacek, R. J., et al., Chem, Phys. Lipids 22 (1978) 163-176]. OLESTRA™ is adaptable to most application where fats and oils are used. However, the major drawback to OLESTRA™is “anal leakage”, the result of a non-digestible fat passing through the digestive system. OLESTRA™ also blocks the absorption of fat soluble vitamins [Bailey's Industrial Oil & fat Products, Vol. 1, Ed. Y. H. Hui (1996), p. 286; Jones D. Y. et al., Amer. J. Clin. Nutr. 53 (1991) 1282-1287 and Dasher, G., et al., FASEB J. 8 (1994) 443].
MCTs are triglycerols composed of C6, C8 and C10 saturated fatty acids. Hunder, J. E., et al., [U.S. Pat. No. 4,863,753 (1989)] reported a low calorie peanut butter containing ≧10% MCTs. A peanut butter composition containing MCTs (41.96%) was reported to have excellent consistency and contained at least 10% fewer calories than the normal fat. However, MCTs may be toxic and may induce metabolic acidosis in large doses [Akoh, C. C. Inform 6 (1995) 1055-1061].
SALATRIM™ (short and long acylglycerol molecules) is a family of structured triacylglycerols prepared by interesterifying a completely hydrogenated vegetable oil with triacetin, tripropionin and/or tributyrin using sodium methoxide as a catalyst at 100-150C [Wheeler, E. L. et al., U.S. Pat. No. 5,258,197 (1991); Klemann, L. P. et al., 42, J. Agr. Food Chem. (1994) 42, 442-446]. Thus, the SALATRIM™ triglycerides are composed of mixtures of long-chain saturated fatty acids (predominantly stearic) and short-chain fatty acids (acetic propionic, and/or butyric) esterified to the glycerol backbone. A similar low calorie fat namely acetyl distearoyl glyceride was prepared by Wheeler, E. L. et al. [U.S. Pat. No. 5,258,197 (1991)]. Extensive testing in animals of SALATRIM™ has shown no changes in the intestinal microflora or secondary bile acids, and no increased mutagenicity or other toxicological effects [Hayes, J. R., et al., J. Agr. Food Chem. 42 (1994) 500-514; Scheinbach, S., et al., ibid, 42 (1994) 572-580; Hayes, J. R., et al., ibid, 42 (1994) 539-551; Hayes, J. R., et al., ibid, 42 (1994) 515-520; and Hayes, J. R., et al., ibid, 42 (1994) 521-527]. However, SALATRIM™ contains unnatural components such as very low molecular weight fatty acids and does not contain essential fatty acids.
Caprenin, a structured triglyceride consisting of caprylic and capric acids and the very long chain behenic acid which was developed for use in chocolate preparation. It yields only 5 cal/g instead of 9 cal/g because the short chain fatty acids have lower energy values and behenic acid is not well absorbed [Peters, J. C. et al., J. Am. Coll. Toxicol. 10 (1991) 357-67; Webb, D. R., et al, ibid 10 (1991) 341-356; Webb, D. R. et al., ibid., 10 (1991) 325-340]. Glycerin was esterified first with behenic acid to form glycerylmonobehenate, which was then reacted with capric and caprylic acids or their anhydrides, and then purified by molecular distillation and steam deodorization. Yoshida, T. et al., [JP 0559392 (1991)] reported the synthesis of 2-behenyl-1,3-dicaproyl glycerol by reacting tribehenin and ethyl caproate in the presence of lipase and the product's feed study on rats showed that absorption of the structured triglycerides was significantly lower and its excretion into feces was higher than other oils. In another report Yoshida R., et al., [Shoka to Kyushu 14 (1991) 27-30 C.A. 117: 47249 (1992)] reported the synthesis of triglycerides with a randomly placed long chain fatty acid (behenic acid) and two medium chain fatty acids (capric and caproic acids) and included it in the diet of rats. These triglycerides were poorly absorbed from the intestine; absorption of behenic acid was particularly poor. Caprenin feeding studies have shown that it produces no toxic effects when fed as the primary source of dietary fat [Webb, D. R. et al., Food Chem. Toxicol. 31 (1993) 935-946]; Webb, D. R., et al., J.Amer. Coll. Toxicol. 10 (1991) 341-356 and Webb, D. R., et al., ibid, 10 (1991) 325-340]. However, a six week study of relative effects on serum lipids and apolipoproteins of a caprenin rich diet feeding studies by Wardlaw, G. M., et al., [Am.J. Clin. Nutr. 61 (1995) 535-542] showed that caprenin can contribute to hypercholesterolemia in men and gastrointestinal complaints in some individuals.